Try this solution on the exchange server itself if you want to hide addresses of disabled users from GAL.
http://serverfault.com/questions/367694/how-to-automatically-remove-disabled-ad-users-from-gal-in-exchange-2010
https://www.petri.com/forums/forum/windows-scripting/powershell/25780-disable-or-enable-user-account-via-powershell-script?postcount=4
Try this if you are talking about just the Auto Complete.
Clearing out the entire auto-complete list.
Important: You are deleting your data. Once it has been deleted, you will not be able to recover it.
Make sure Outlook 2011 is closed.
Open up "Finder" and navigate to /Documents/Microsoft User Data/Office 2011 Identities/Main Identity/Data Records/Recent Addresses/0T/0B/0M/0K/.
*Note: Each "/" in the path above represents a break between screens.
In this folder, there will be a file named, or similarly named to, x19_4.olk14Recent, delete this item.
Open Outlook. You will receive an error indicating a problem with the Office database. Click Rebuild.
After the rebuild is complete, hit the Done button and close the "Microsoft Database Utility" window.
https://kb.wisc.edu/office365/page.php?id=48716#mac
Thanks for the reply @Eigger. The auto complete did the trick. This page also helped immensely. I just used a quick script to target the Office Identity folder and ran a recursive find along with a deletion of the database file. Restart outlook and its gone.
This is an example for the Office 2016 Outlook.
cd ~/Library/Group Containers/
find . -name "*.olk15RecentAddresses" -type f|xargs rm -f
@danshaw Hey man.. using that script yields no results for me. It doesn't delete any file. Do you have an updated script you use aside from what you posted above?
@ooshnoo I just re-ran the script and it still works fine for me. Open up terminal and type in each line to test. I didn't want to delete mine so I typed in the line below and it returned the location of that recent addresses file. The "rm -f" just deletes it.
find . -name "*.olk15RecentAddresses" -type f|xargs
Returns:
./UBF8T346G9.Office/Outlook/Outlook 15 Profiles/Main Profile/Data/Recent Addresses/253/FDFB163B-4AD8-4993-8E35-0C2D781C238C.olk15RecentAddresses